Heartbeat irregularity in athletes appears benign

NEW YORK (Reuters Health) - A new study offers more evidence that the rapid heartbeat seen in many hard-training athletes is typically a benign side effect of physical conditioning.

Elite athletes usually have lower-than-normal heart rates when at rest, but when they are active, some develop rapid heart rhythms known as ventricular tachyarrhythmias. Studies suggest that up to 30 percent of high-level athletes show irregular ventricular rhythms.

In the absence of any underlying heart abnormality, these rhythm irregularities are thought to stem from the effects of training and are considered to be a part of a benign condition known as "athlete's heart."

Another feature of athlete's heart is an enlargement of the heart's main pumping chamber, known as left ventricular hypertrophy, or LVH.

In non-athletes, pathological LVH usually increases the risk of ventricular tachyarrhythmias as it worsens. So in the current study, Italian researchers looked at whether there is a similar relationship in elite athletes.

The researchers outfitted 175 Olympic and world-class athletes with portable monitors that recorded their heart's electrical activity over 24 hours. They also had them undergo ultrasound scans to detect LVH.

Overall, the researchers found, 14 percent of the study group had evidence of LVH. But there was no indication that LVH raised the risk of ventricular tachyarrhythmias, the researchers report in the American Journal of Cardiology.

The findings suggest that, in contrast to pathological cases, the ventricular arrhythmias seen in elite athletes are not caused by LVH-induced changes in the heart's electrical activity, according to the researchers, led by Dr. Alessandro Biffi, of the Italian Olympic Committee in Rome.

Instead, they say, alterations in nervous system activity, brought on by high-level athletic training, may be responsible. In support of this, past research has shown that ventricular tachyarrhythmias decline once athletes stop training and playing at a competitive level.

These latest findings, Biffi and colleagues write, "offer a measure of clinical reassurance regarding the benign nature of ventricular tachyarrhythmias in elite athletes and the expression of athlete's heart."

SOURCE: American Journal of Cardiology, June 15, 2008.